The present invention relates to a new and improved method of casting or pouring steel into a continuous casting mold wherein the steel is introduced by means of a pouring tube into the casting head i.e. the liquid metal pool to a location beneath the level of such liquid metal pool in the mold and the steel prior to its departure out of the pouring tube is treated with an inert gas while forming small bubbles, and furthermore, this invention also relates to a new and improved construction of apparatus for the performance of the aforesaid method.
In order to improve upon separation of nonmetallic inclusions during continuous casting operations it is known to the art to arrange beneath an outflow nozzle of a tundish a chamber-like device into which the casting jet flows in a freefall. This chamber possesses lateral openings through which the casting jet flows into the liquid metal pool after experiencing a change in flow direction which is brought about by the floor of the chamber. By destroying a part of the kinetic energy and the resultant reduction in the flow velocity it is intended to provide an easier separation of the contaminants. By infeeding oxidizing or inert gases into the intermediate space between the casting jet and the chamber walls it is further intended to influence the composition of the inclusions. However, this prior art technique neither is intended to nor does it influence the formation of the flow at the casting head by means of the gas which likewise flows through the chamber. There also does not occur any appreciable admixing with the gas. Additionally, such prior art apparatus is associated with the drawback that it is relatively expensive and difficult to use.
Furthermore, it is known to the art to treat the casting jet with the gas bubbles and to introduce such beneath the level of the molten metal bath of the mold by means of an immersed pouring tube having oval or circular outlet openings. Thus, the gas is delivered to the steel at the location of the formation of the casting jet, for instance above the stopper. Although according to this proposal there is realized a qualitative improvement of the cast product, still it has not been possible to influence the flow conditions at the casting head in such a way that there is realized an optimum possibility of separating out the inclusions.